I am making a game about a worm and for now all the art is pixel art but I would like to switch to smooth vector art. Does anybody know what free websites/apps I could use? Thank you!

Try SVG-edit for a start, and Inkscape when you want to get serious about it. You can also code SVG by hand. (The MDN website has more information about that.)Unfortunately I don't know of any dedicated communities, but people post vector art in this category often enough.